What is it is an element or something more

An element is a substance that is made entirely from one type of atom.

Explanation:

For example, the element hydrogen is made from atoms containing a single proton and a single electron.

Please mark me the brainliest!?!

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.

6.4 cm (max) - 25 cm (min)